Kinetic Studies of the Thermal cis-to-trans Isomerization of Dioxaphospholanes

By following a previously reported method,¹ the synthesis of r-2-alkoxy-cis-4-cis-5-dimethyl-1,3,2-λ³-dioxaphospholanes ligands (1 and 3) was carried out. The purpose of this work is the kinetic study of the inversion barrier at phosphorus for 1 and 3 and the comparison with the already informed dioxaphospholane 2. The kinetic measurements of the thermal isomerization cis-to-trans were performed by ³¹P NMR spectroscopy, observing a first order kinetics for both compounds. The energy of activation (E_a) for the epimerization of compounds cis-1 and cis-3 was calculated to be 16.0 ± 0.6 and 11.8 ± 0.8 kcal/mol, respectively. The values of the thermodynamic parameters of the transition state (Δ H^≠, Δ S^≠, Δ G^≠) suggest that the inversion at phosphorus not only depends on the spatial requirements of the alkoxy substituent but also on entropic effects. The thermodynamic parameters Δ H°, Δ S°, and Δ G° were also evaluated and they show that the cis isomers are preferred from enthalpic point of view, but entropic effects dominate the equilibrium trans ? cis leading to the entropically favored trans isomers. Furthermore, the results are supported by density functional theory calculations of 1–4 at the B3LYP/6-31G** level.     

柠檬酸配合法制备CuMnCeOx催化剂及常温催化氧化性能研究

摘要：常温催化氧化是消除室内HCHO污染最可行的方法之一,其中以过渡金属氧化物为代表的催化剂因性能优异、成本低廉而备受广泛关注。采用柠檬酸络合法和水热法制备了一系列CuMnCeOx催化剂,研究考察制备方法及载体对催化剂氧化性能的影响,并利用XRD、SEM、BET、H2-TPR、XPS和IR等对催化剂进行微观表征与分析。研究发现,制备方法及载体类型对催化剂的表面结构形貌、氧化性能产生显著影响,其中采用柠檬酸络合法所制的CuMnCeOx-C催化剂性能最佳,48h的HCHO去除率达98.6%,完全满足GB50325-2001标准要求,其介孔结构,晶体粒径及所形成的铈基铜锰固溶体均利于形成大量氧空位及催化氧化反应,且展示出良好的抗水蒸气和稳定性能,其在常温催化氧化VOCs方面具有重要应用前景。     

Relaxation dynamics and fragility during liquid–glass transitions of poly(propylene glycol)s

The acoustic and thermal properties of the liquid–glass transitions of propylene glycol and its oligomers, poly (propylene glycol)s, were studied by temperature modulated DSC and Brillouin scattering. The fragility indices were determined from Angell plots using the observed modulation frequency dependence of the complex heat capacity. The variation in the glass transition temperatures is discussed on the basis of the free volume theory. The relaxation time of the structural relaxation obeys the Vogel–Fulcher law, and its high frequency end is in good agreement with the result of the dielectric measurement in the literature. The correlation between the observed thermal expansion coefficients and the glass transition temperature is discussed based on the free volume theory. The sound velocity and attenuation were accurately determined as a function of the temperature by Brillouin scattering by combination with the refractive index measurement. The relaxation dynamics were discussed by considering the relaxation from segmental motions. All of these physical properties were discussed based on the third-order anharmonicity and the Grüneisen parameter.     

尿素作为添加剂低温制备高活性的TiO2光催化剂

以钛酸丁酯为原料,尿素作为添加剂,在酸性水溶液中室温制备了稳定透明的TiO2水溶胶。经过300℃低温焙烧2 h,得到了由锐钛矿和金红石组成的TiO2混晶。用XRD、FT-IR对催化剂进行了表征。以甲基橙为降解对象研究了TiO2的光催化活性,实验结果显示所制备的TiO2具有比Degussa P25更高的催化活性,15m in后的降解率达到了78%(P25,58%)。考察了尿素添加量以及焙烧温度对TiO2催化性能的影响,当尿素与钛酸丁酯物质的量之比为3∶1,300℃下焙烧2 h为较适宜的催化剂制备条件。初步探讨了尿素作为添加剂在低温制备高活性TiO2过程中的作用。     

有限深水域中三维频域自由面格林函数及其导数的计算方法

三维频域自由面格林函数及其偏导数的数值计算是海洋结构物水动力分析的难点.本文对有限水深格林函数及其偏导数的数值算法作出两点改进:①对原函数的级数表达式进行变形,提出适用于数值计算的形式,解决高频率情况下级数解的计算失真问题;②对Gauss-Laguerre积分法作出改进,解决高频率大水深情况下积分解的数值溢出问题.计算...     

塑料光纤纤端光场测试结果及分析

对纤端光场进行了理论分析,分别利用塑料光纤和多模光纤作为接收光纤对塑料光纤的出射纤端光场进行了测量,并与理论分析结果进行了比较,给出了合理的调和参数.传输距离较长的塑料光纤由于高阶模的泄漏,纤端光场分布非常接近高斯分布.实验结果表明了理论分析结果和调和参数选择的合理性.     

人肝癌细胞系HLE细胞表面抗原多肽的纳升电喷雾串联质谱从头测序分析

肿瘤细胞表面的抗原多肽能够被细胞毒T淋巴细胞特异性识别而引起免疫应答,因此有可能用于研制基于多肽的抗肿瘤疫苗。用弱酸将人肝癌细胞系HLE细胞表面抗原多肽和人正常肝细胞表面多肽洗脱后,经RP-HPLC分离,选择HLE细胞表面特异性多肽进行纳升电喷雾串联质谱(nanoESI-MS/MS)测序,共测定5个色谱峰中的20个多肽序列,分子量分布范围为1000~2000 Da。借助M asSeq软件分析出其中12个多肽的序列。经数据库查寻,其中的3个肽段分别来自钙调节蛋白、核蛋白S19和伴侣蛋白10。这些多肽的生物学功能及与肿瘤的关系值得深入研究。该研究表明nanoESI-MS/MS是测定微量混合多肽序列的最有效方法。     

建筑结构动力特性动点脉动测试

介绍用无人工激励动点测试（动点脉动测试）方法确定建筑物的自振频率，振型和阻尼。使用这一方法对南京电视塔、多层基础隔振房屋及水塔等进行了动力性能测试，获得了满意的结果。     

中国的百岁老人研究Ⅱ.百岁老人的死亡率、生存率和发展趋势

根据全国人口普查资料,用指数函数拟合法计算了中国百岁老人的死亡率和生存率,得出中国人口的最高自然寿限为120岁,并预测到2010年中国百岁老人绝对数将达4万多人,届时每百万人口中将有30位百岁老人,比2000年增加1倍以上。     

掺杂铕和铽的卤硼酸盐荧光体的制备及光谱特征

采用高温固相法在空气中合成了一系列掺杂稀土离子的卤硼酸盐荧光体, 研究了其发光性质和基质组成对稀土离子共掺杂的荧光体发光性质的影响. 研究结果表明, 在Eu3+和Tb3+共掺杂的体系中存在电子转移, 因此出现了Eu3+, Eu2+和 Tb3+共存于同一基质共同发射的现象. Ce3+对Eu2+和Tb3+具有敏化作用, 可增强其发射强度. 基质的组成对稀土离子的发射峰位和发射强度有明显影响.